diff --git a/lib/httpx/request.rb b/lib/httpx/request.rb
index 1a0984aa..58d10d8f 100644
--- a/lib/httpx/request.rb
+++ b/lib/httpx/request.rb
@@ -83,7 +83,7 @@ module HTTPX
 
       @options = @body.options
 
-      if @uri.relative?
+      if @uri.relative? || @uri.host.nil?
         origin = @options.origin
         raise(Error, "invalid URI: #{@uri}") unless origin
 
diff --git a/test/support/requests/errors.rb b/test/support/requests/errors.rb
index ba1cca46..3993b903 100644
--- a/test/support/requests/errors.rb
+++ b/test/support/requests/errors.rb
@@ -2,6 +2,13 @@
 
 module Requests
   module Errors
+    def test_errors_invalid_uri
+      exc = assert_raises { HTTPX.get("/get") }
+      assert exc.message.include?("invalid URI: /get")
+      exc = assert_raises { HTTPX.get("http:/smth/get") }
+      assert exc.message.include?("invalid URI: http:/smth/get")
+    end
+
     def test_errors_connection_refused
       unavailable_host = URI(origin("localhost"))
       unavailable_host.port = next_available_port